JP2004292261A - Catalytic reactor for fuel reforming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalytic reactor which can maintain heat exchanging properties without depending on the variation of operating conditions. <P>SOLUTION: The catalytic reactor is provided with: a catalytic reaction layer 3a causing exothermic reaction by using a reaction gas to be fed; and a refrigerant layer 3b in which a fluid circulates and which is heat-exchangeable with the catalytic reaction layer 3a. The catalytic reactor is further provided with a dryness determination means of determining the dryness of the fluid circulating through the refrigerant layer 3b, in this case a comparing means (S2) of comparing the temperature of steam exhausted from the refrigerant layer 3b detected by a temperature sensor 4 with a prescribed temperature. The catalytic reactor is still further provided with: a dryness control means of controlling the dryness of the fluid on the basis of the determination result of the dryness, in this case a flow rate control valve 2 of controlling the flow rate of the fluid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a catalytic reactor for a fuel reforming system. In particular, it relates to temperature control in a catalytic reactor.
[0002]
[Prior art]
As a catalytic reaction device for a fuel reforming system having a catalytic reaction layer that generates an exothermic reaction, one that maintains high reaction efficiency by adjusting the temperature of the catalytic reaction layer by performing heat exchange with steam is known. ing.
[0003]
In the catalytic reaction layer for reducing carbon monoxide in the hydrogen-rich gas, it is necessary to operate in a predetermined temperature range in order to increase the carbon monoxide reduction efficiency. In the shift reaction in which carbon dioxide and hydrogen are generated by the reaction between carbon monoxide and moisture, the predetermined temperature range is about 300 ° C to 200 ° C. In a selective oxidation reaction in which carbon dioxide is generated by a reaction between carbon monoxide and oxygen, a predetermined temperature range is about 200 ° C to 100 ° C.
[0004]
In such a catalytic reactor, the temperature of a catalytic reaction layer that reduces carbon monoxide in a hydrogen-rich gas obtained by reforming hydrocarbon fuel is controlled by heat exchange with wet steam in a gas-liquid two-phase state. I do. Thus, the temperature of the catalyst reaction layer can be adjusted to a predetermined temperature range, and the carbon monoxide reduction efficiency and the thermal efficiency can be maintained high (for example, see Patent Documents 1 and 2).
[0005]
[Patent Document 1]
JP 2001-163601 A
[Patent Document 2]
JP 2002-47002 A
[0006]
[Problems to be solved by the invention]
However, in the above-mentioned catalytic reaction device, the dryness of steam varies due to the variation in the operating load, and the heat exchange characteristics of the refrigerant layer may fluctuate rapidly. In particular, when the endothermic heat from the catalytic reaction layer is insufficient, there are portions where the reaction temperature deviates from a predetermined range. For this reason, there has been a problem that it may be difficult to maintain the carbon monoxide reduction efficiency sufficiently high.
[0007]
In view of the above problems, an object of the present invention is to provide a catalytic reactor capable of maintaining heat exchange characteristics regardless of a change in an operating load.
[0008]
[Means for solving the problem]
The present invention provides a catalyst reaction layer that generates an exothermic reaction using a supplied reaction gas, a fluid layer in which a fluid flows, and a heat exchange layer with the catalyst reaction layer, and a fluid layer that flows through the refrigerant layer. Dryness determination means for determining the degree. The apparatus further includes a dryness adjusting unit that adjusts the dryness of the fluid based on the dryness determination result.
[0009]
Alternatively, it includes a catalytic reaction layer capable of removing carbon monoxide, and a refrigerant layer through which a fluid flows and capable of exchanging heat with the catalytic reaction layer. The degree of dryness of the fluid flowing through the refrigerant layer is adjusted so that the refrigerant layer is maintained at a temperature suitable for the reaction efficiency.
[0010]
[Action and effect]
The dryness of the fluid flowing through the refrigerant layer is determined, and the dryness of the fluid is adjusted based on the determination result of the dryness. This makes it possible to stabilize the heat exchange characteristics of the refrigerant layer irrespective of fluctuations in the operating load.
[0011]
Alternatively, the dryness of the fluid flowing through the refrigerant layer is adjusted so that the catalyst reaction layer is maintained at a temperature suitable for the reaction efficiency. As described above, by adjusting the dryness of the fluid, the heat exchange characteristics can be stabilized, and the temperature of the catalyst reaction layer can be maintained at a temperature suitable for the reaction, so that the reaction efficiency in the catalyst reaction layer is maintained at a high level. be able to.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
As a catalytic reaction device for a fuel reforming system used in the first embodiment, a CO reduction device 1 having a schematic configuration as shown in FIG. 1 is used. Here, in particular, the CO reduction device 1 is a shift reaction device that reduces CO in the hydrogen-rich gas by a shift reaction.
[0013]
By preheating water, H in gas-liquid two-phase state ₂ The apparatus includes a water preheating device (not shown) that generates O (hereinafter, wet steam), and a flow control valve 2 that controls the flow rate of wet steam generated by the water preheating device (not shown). The shift reactor 3 for reducing CO in the hydrogen-rich gas and performing heat exchange between the hydrogen-rich gas and steam, and a pressure reducing valve 5 for adjusting the pressure of steam flowing through the shift reactor 3 are provided. Further, as will be described later, a temperature sensor 4 for detecting the temperature of steam discharged from the shift reactor 3 and a controller 20 for controlling the CO reduction device 1 are provided. Here, the term “water vapor” includes both a state of wet vapor composed of a gas-liquid two-phase state and a state of dry vapor composed of only a gas phase.
[0014]
The shift reactor 3 is composed of a catalyst reaction layer 3a and a refrigerant layer 3b arranged so as to be able to exchange heat with the catalyst reaction layer 3a. In the catalyst reaction layer 3a, a shift reaction (CO + H) is performed at about 300 ° C. to 200 ° C. ₂ O → H ₂ + CO ₂ ) Is charged with a catalyst to be activated. For example, the catalyst Cu / ZnO is filled. By flowing a hydrogen-rich gas through such a catalytic reaction layer 3a, the CO concentration in the hydrogen-rich gas is reduced. The catalyst layer 3a is adjusted to an appropriate reaction temperature range by flowing steam through the refrigerant layer 3b and absorbing heat accompanying the shift reaction generated in the catalyst reaction layer 3a. The reaction temperature range and the type of catalyst are not limited to the above.
[0015]
Next, the hydrogen-rich gas system 15 in the CO reduction device 1 will be described. The hydrogen-rich gas system 15 serves as a hydrogen-rich gas flow path including a means for supplying the hydrogen-rich gas to the catalyst reaction layer 3a of the shift reactor 3.
[0016]
In a fuel reformer (not shown), a hydrogen-rich gas is generated from the hydrocarbon fuel, steam, and oxidant. For example, desulfurized gasoline is used as a hydrocarbon fuel, and air is used as an oxidant. The hydrogen-rich gas generated in the fuel reformer contains CO that causes deterioration of a catalyst such as platinum provided in a fuel cell (not shown). Therefore, in a high-temperature shift reactor (not shown), a shift reaction is caused to reduce CO in the hydrogen-rich gas to about 2%.
[0017]
The hydrogen-rich gas having the reduced CO concentration is supplied to the CO reduction device 1. The hydrogen-rich gas is supplied to the catalytic reaction layer 3a provided in the shift reactor 3 of the CO reduction device 1. When the hydrogen-rich gas flows through the catalyst reaction layer 3a, a shift reaction further occurs, and the CO concentration is reduced to about 0.5%. At this time, heat is generated along with the shift reaction, but this heat is absorbed by the refrigerant layer 3b, so that the catalytic reaction layer 3a is maintained in a predetermined temperature range.
[0018]
The hydrogen-rich gas in which CO has been reduced in the shift reactor 3 is further supplied to a selective oxidation reactor (not shown). When the hydrogen-rich gas flows through the selective oxidation reactor, the selective oxidation reaction of CO (CO + 1 / 2O) ₂ → CO ₂ ) Occurs, and the CO concentration in the hydrogen-rich gas is reduced to about 10 ppm. Thereafter, it is supplied to a fuel cell (not shown) and used for power generation.
[0019]
Next, the steam system 17 for adjusting the temperature of the catalytic reaction layer 3a provided in the CO reduction device 1 will be described. Here, the steam system 17 is a steam flow path including means for supplying gas-liquid two-phase wet steam to the refrigerant layer 3b of the shift reactor 3.
[0020]
Steam is generated in a water preheating device (not shown). At this time, the water vapor is generated in a wet vapor state in a gas-liquid two-phase state. The generated wet steam is supplied to the refrigerant layer 3b of the shift reactor 3 after the flow rate is adjusted by the flow rate adjusting valve 2. Here, as means for adjusting the flow rate of the wet steam, a pump may be used instead of the flow rate control valve 2. In this case, the flow rate of the wet steam is adjusted by adjusting the discharge amount of the pump.
[0021]
The moist steam absorbs reaction heat generated in the catalyst reaction layer 3a when flowing through the refrigerant layer 3b, thereby maintaining the temperature of the catalyst reaction layer 3a in a predetermined temperature range. Here, the steam pressure in the coolant layer 3b is adjusted by adjusting the pressure reducing valve 5 provided downstream of the coolant layer 3b, so that the steam temperature is adjusted to a temperature suitable as a coolant. For example, the pressure is increased to about 1 MPa to raise the boiling point to 180 ° C. Thereby, the H of the liquid phase in the wet steam flowing through the refrigerant layer 3b is ₂ The catalytic reaction layer 3a can be efficiently cooled using sensible heat when O changes into a gas phase. At this time, H ₂ By setting the amount of preheating in a water preheating device (not shown) so that O does not become dry steam consisting only of a gas phase due to reaction heat absorbed from the catalyst reaction layer 3a, the steam temperature can be adjusted to about the boiling point. it can. With respect to the fluctuation of the flow rate of the hydrogen-rich gas according to the load fluctuation, that is, the fluctuation of the heat generated in the catalyst reaction layer 3a, the flow rate of the steam flowing through the refrigerant layer 3b is adjusted by adjusting the flow rate control valve 2; This prevents the steam from being dried and becoming a steam state, thereby reducing the heat exchange efficiency. At this time, since the steam is used for the reforming reaction in the subsequent process, the steam flow rate is adjusted so that a large amount of the liquid phase is not contained in the steam discharged from the refrigerant layer 3b.
[0022]
The steam used for controlling the temperature of the catalytic reaction layer 3a is supplied from the refrigerant layer 3b to the fuel reformer via the pressure reducing valve 5, and used for the reforming reaction. Here, a steam generation device or the like (not shown) may be provided, and the steam flow rate may be adjusted by the flow rate control valve 2 so as to compensate for the shortage of steam for performing the required reforming reaction.
[0023]
Next, a method for correcting the steam flow rate will be described with reference to the flowchart in FIG.
[0024]
In the present embodiment, the state of wet steam is maintained by adjusting the steam dryness by correcting the steam flow rate. The opening α of the flow control valve 2 for adjusting the steam flow rate is basically the standard opening α at the operating load. ₀ , But is corrected according to the load fluctuation. Here, the degree of dryness of the steam discharged from the refrigerant layer 3b and, consequently, the temperature of the steam change according to the load change, and the opening α is adjusted accordingly. Standard opening α ₀ In advance, the opening degree characteristic corresponding to the operating load is obtained in advance through experiments or the like, and this is made into a map or a mathematical expression and stored in the controller 20. Hereinafter, a method of correcting the steam flow rate will be described.
[0025]
Here, since the preheating amount and the steam flow rate according to the operating load are set, when a change in the operating load is detected, the opening α is changed to the basic opening α according to the operating load. ₀ After this setting, this control is repeatedly performed during the operating load transition period. During the transition period of the operation load, the balance between the heat generated by the shift reaction using the hydrogen-rich gas and the flow rate of the steam flowing through the refrigerant layer 3b may be lost. In contrast, by correcting the opening α of the flow control valve 2 as described below, the dryness of the steam in the refrigerant layer 3b can be adjusted.
[0026]
In step S1, the temperature sensor 4 reads a temperature detection value T of water vapor discharged from the refrigerant layer 3b. Here, the dryness of the steam in the refrigerant layer 3b is estimated according to the magnitude of the detected value T of the steam temperature. In step S2, the detected value T and the target value T ₀ Compare with. Where the target value T ₀ Is a temperature suitable for a refrigerant for adjusting the temperature of the catalytic reaction layer 3a to an appropriate reaction temperature range, in which the dryness of steam does not become 1. The dryness indicates the ratio of the mass of the dry saturated steam to the total mass of the steam per unit volume. For example, when the dryness is close to 1, it indicates a state of a spray flow in which droplets are flowing in a spray state in a gas flow. When the dryness is near 0, it indicates a bubble flow state in which bubbles are flowing in the liquid flow. When the dryness of the steam becomes 1, the heat absorption by the sensible heat of water cannot be used to cool the catalytic reaction layer 3a, so that the heat absorption efficiency is rapidly reduced. In order to maintain the cooling efficiency by steam, the target temperature T ₀ At a pressure of the refrigerant layer 3b, 1 MPa in this case, at a temperature at which water vapor consists of a two-phase flow of a gas phase and a liquid phase and can be used as a refrigerant. Target value T ₀ Is most preferably the boiling point of water.
[0027]
Further, when it is assumed that steam is used as a reforming raw material of the fuel reformer in the process after flowing out of the refrigerant layer 3b, it is not desirable to discharge a large amount of unvaporized water. Therefore, in the present embodiment, the target value T is set with a margin so as to prevent a large amount of unvaporized water from flowing out. ₀ To a temperature slightly higher than the boiling point of water. Specifically, since the boiling point of water in the refrigerant layer 3b is set to 180 ° C., the target value T ₀ To 190 ° C.
[0028]
In step S2, T <T ₀ In the case of, it can be estimated that the degree of dryness of steam is small and a large amount of unvaporized water may be present. Therefore, the process proceeds to step S3, in which the opening α of the flow control valve 2 is reduced. Thereby, the flow rate of steam for performing heat exchange in the refrigerant layer 3b is reduced, so that the amount of heat absorbed by the steam per unit flow rate is increased, and the presence of unvaporized water can be reduced. This corresponds to, for example, a transition period in which the operating load increases.
[0029]
On the other hand, in step S2, T> T ₀ In the case of (1), it can be estimated that the degree of drying of the steam becomes 1, and the heating temperature of the steam becomes excessive, and the temperature control of the catalytic reaction layer 3a may be insufficient. When the dryness of the steam becomes 1, the heat exchange efficiency of the steam is remarkably reduced, so that the catalyst reaction layer 3a may not be sufficiently cooled. Therefore, the process proceeds to step S4, and the opening α of the flow control valve 2 is increased. Thereby, the absorption of heat from the catalytic reaction layer 3a can be promoted by increasing the flow rate of steam supplied to the refrigerant layer 3b. This corresponds to, for example, a transition period in which the operating load decreases.
[0030]
On the other hand, in step S2, T = T ₀ In this case, the state of steam is preferable, and the temperature of the catalytic reaction layer 3a can be sufficiently adjusted, so that the opening degree α is maintained as it is. After correcting the opening degree α of the flow control valve 2 in this way, the present flow is terminated. This corresponds to, for example, a case where the fluctuation of the operation load is gentle.
[0031]
By repeatedly performing the above-described control, the steam temperature can be controlled even when the load changes, and the dryness of the steam can be maintained. If the dryness of steam changes due to other operating conditions of load fluctuation, the above-described control may be repeatedly performed during the operation of the fuel reforming system.
[0032]
Next, the internal temperature distribution of the CO reduction device 1, particularly the shift reactor 3, will be described. FIG. 3A shows a conventional internal temperature distribution, and FIG. 3B shows an internal temperature distribution in the present embodiment.
[0033]
Conventionally, a region where the degree of dryness of steam is 1 becomes large in the refrigerant layer 3b due to a change in operating conditions. In a region where the water vapor is dry, the heat transfer coefficient is sharply reduced, so that the heat passage from the catalytic reaction layer 3a to the refrigerant layer 3b is sharply reduced. In the region where heat transfer is reduced, the reaction temperature may be higher than the optimal range, and the side reaction, the reverse shift reaction (CO 2 ₂ + H ₂ → CO + H ₂ The reaction rate of O) increases. Therefore, the CO reduction efficiency cannot be sufficiently increased.
[0034]
On the other hand, in the present embodiment, the region where the water vapor dries is minimized (T ₀ = Zero when the opening α is corrected as the boiling point of water), so that the heat passage from the catalytic reaction layer 3a to the refrigerant layer 3b is maintained high. Thereby, the temperature of the catalyst reaction layer 3a is maintained in an optimum range for the reaction, so that the reverse shift reaction, which is a side reaction, is suppressed. Thereby, the CO reduction efficiency can be increased.
[0035]
Next, effects of the present embodiment will be described.
[0036]
A catalytic reaction layer 3a that generates an exothermic reaction using the supplied reaction gas, and a medium layer 3b through which a fluid flows and that can exchange heat with the catalytic reaction layer 3a. The apparatus includes dryness determining means for determining the dryness of the fluid flowing through the refrigerant layer 3b, and dryness adjusting means for adjusting the dryness of the fluid based on the determination result of the dryness. Thereby, the dryness of the fluid, here the dryness of the steam, can be adjusted to a predetermined value. Therefore, the steam can be set to a wet steam state, and the heat exchange characteristics of the refrigerant layer 3b can be stabilized. Further, by preventing the dryness of the steam from becoming an excessively small value, it is possible to prevent a large amount of the liquid phase from being included in the steam discharged from the refrigerant layer 3b.
[0037]
As the dryness determining means, a temperature comparing means (S2) for determining the dryness of the fluid by comparing the temperature of the fluid flowing out of the refrigerant layer 3b, here the steam temperature, with a predetermined temperature is provided. As the predetermined temperature, a temperature at which the dryness is smaller than 1 and at which the catalyst reaction layer 3a can be adjusted to an appropriate temperature is set. Here, in order to prevent a large amount of liquid water from being present in the subsequent process, a value slightly larger than the boiling point of the fluid is set as the predetermined temperature. Thus, the dryness of the steam can be determined with a simple configuration.
[0038]
As the dryness adjusting means, the fluid temperature is adjusted so that the temperature of the fluid flowing out of the refrigerant layer 3b is at least a predetermined value equal to or higher than the phase change temperature of the fluid. By adjusting the temperature of the fluid in this way, the dryness of the fluid can be appropriately adjusted.
[0039]
As described above, whether the dryness of the steam is appropriate is determined by detecting the steam temperature, and if it is determined that the steam is not appropriate, the dryness of the steam is adjusted by adjusting the steam temperature. This makes it possible to suppress the region where the degree of dryness of the water vapor in the refrigerant layer 3b is 1 in the refrigerant layer 3b with a simple configuration, and to stably stabilize the heat exchange characteristics. For example, by adjusting the steam temperature so that the detected temperature becomes the phase change temperature of the steam, the region where the dryness becomes 1 can be made zero.
[0040]
As a temperature control means, a flow control valve 2 for controlling the flow rate of steam flowing through the refrigerant layer 3b is provided. Thus, the dryness of the steam can be adjusted to a predetermined value with a simple configuration, and the heat exchange characteristics of the refrigerant layer 3b can be stabilized.
[0041]
In the catalyst reaction layer 3a, carbon dioxide and hydrogen are generated by a reaction between CO and water. That is, a shift reaction device is used as the CO reduction device 1. This makes it possible to appropriately adjust the temperature of the shift reaction and increase the reaction efficiency of the shift reaction.
[0042]
As the fluid flowing through the refrigerant layer 3b, steam as a raw material for producing a hydrogen-rich gas is allowed to flow in a gas-liquid two-phase state. As a result, the reaction heat generated in the catalytic reaction layer 3a is absorbed by the water vapor, which is a raw material for producing a hydrogen-rich gas, so that a means for dissipating the reaction heat is not required and the apparatus configuration can be simplified. In addition, the reaction heat in the CO reduction device 1 can be used as a part of the heat for generating the steam used for the reforming reaction, so that the thermal efficiency of the system can be improved.
[0043]
A catalytic reaction layer 3a capable of removing CO, and a refrigerant layer 3b through which a fluid, here, steam flows, and which can exchange heat with the catalytic reaction layer 3a. The dryness of the steam flowing through the refrigerant layer 3b is determined. , So that the refrigerant layer 3b is maintained at a temperature suitable for the reaction efficiency. Thereby, the degree of dryness can be adjusted so that the heat exchange characteristics of the refrigerant layer 3b can be stabilized, and the temperature of the catalytic reaction layer 3a can be adjusted such that the CO reduction efficiency is kept high.
[0044]
Next, a second embodiment will be described. Hereinafter, a description will be given focusing on portions different from the first embodiment.
[0045]
FIG. 4 shows a schematic configuration of the catalytic reaction device. In the first embodiment, a CO reduction device 1 including a shift reactor 3 is used as a catalytic reaction device, whereas a CO reduction device 7 including a selective oxidation reactor 6 is used here.
[0046]
The selective oxidation reactor 6 is composed of a catalytic reaction layer 6a and a refrigerant layer 6b arranged so as to be able to exchange heat therewith. In the catalyst reaction layer 6a, the selective oxidation reaction (2CO + O ₂ → 2CO ₂ ) Is charged with a catalyst to be activated. For example, the catalyst Ru / Al ₂ O ₃ Fill. The reaction temperature range and the type of catalyst are not limited to the above.
[0047]
The configuration of the hydrogen-rich gas system 15 in the CO reduction device 7 having such a configuration will be described.
[0048]
Hydrogen-rich gas generated by causing a reforming reaction in a fuel reformer (not shown) is supplied to a shift reactor (not shown), and the CO concentration is reduced to about 0.5% by the shift reaction. Thereafter, air as an oxidizing agent is mixed in by an air supply device, and then supplied to the catalytic reaction layer 6a of the selective oxidation reactor 6. Here, CO is reduced to about 10 ppm by causing a selective oxidation reaction accompanied by heat generation. The reaction heat generated at this time is absorbed by the refrigerant layer 6b, so that the catalyst reaction layer 6a is maintained at a predetermined temperature.
[0049]
The hydrogen-rich gas having a reduced CO concentration is supplied to a fuel cell (not shown) and used for a power generation reaction.
[0050]
On the other hand, the steam system 17 is the same as in the first embodiment. However, here, the pressure of the refrigerant layer 6b adjusted by the pressure reducing valve 5 is set lower than that of the first embodiment in order to make the temperature of the wet steam suitable as the refrigerant. For example, the pressure is increased to about 0.5 MPa, and the boiling point is set to about 150 ° C.
[0051]
Target value T ₀ Is preferably the boiling point of water. However, in the present embodiment, a large amount of unvaporized water does not flow out in the subsequent process. ₀ To a temperature slightly above the boiling point. Specifically, the temperature is set to 160 ° C.
[0052]
With this configuration, a temperature distribution as shown in FIG. 3 can be obtained as in the first embodiment.
[0053]
Next, effects of the present embodiment will be described. Hereinafter, only the effects different from those of the first embodiment will be described.
[0054]
In the catalytic reaction layer 6a, carbon dioxide is generated by the reaction between CO and oxygen. That is, a selective oxidation reaction device is used as the CO reduction device 7. Thereby, the temperature of the selective oxidation reaction can be appropriately adjusted, and the reaction efficiency of the selective oxidation reaction can be increased.
[0055]
Next, a third embodiment will be described. Hereinafter, a description will be given focusing on portions different from the second embodiment. In the second embodiment, the steam flow rate is adjusted in order to maintain the steam as wet steam, but here, the dryness of the steam in the refrigerant layer 6b is adjusted by adjusting the steam pressure.
[0056]
A CO reduction device 8 having a selective oxidation reactor 6 is used. FIG. 5 shows the configuration of the CO reduction device 8.
[0057]
Here, since the correction of the steam flow rate is not performed, the flow control valve 2 arranged on the upstream side of the refrigerant layer 6b is omitted. Further, a pressure control valve 10 is provided downstream of the refrigerant layer 6b instead of the pressure reducing valve 5. A temperature sensor 4 and a pressure sensor 9 are provided between the refrigerant layer 6b and the pressure control valve 10.
[0058]
The pressure of the steam is basically adjusted by the opening degree β of the pressure control valve 10 with a target value at which the temperature at which the wet steam becomes a temperature suitable for the refrigerant. Here, it is adjusted to, for example, 0.5 MPa. Since the flow rate of steam flowing in accordance with the required load changes, the basic opening degree β is set so that the refrigerant layer 6b is always about 0.5 MPa in accordance with the required load. ₀ Set. However, the pressure of the refrigerant layer 6b is corrected according to the detected value T of the temperature sensor 4. This correction will be described with reference to the flowchart of FIG. When it is detected that there is a change in the required load, the pressure control valve 10 is set to the basic opening degree β corresponding to the required load. ₀ And then start this flow.
[0059]
In step S11, the temperature detection value T of the steam discharged from the refrigerant layer 6b is read using the temperature sensor 4. In step S12, the pressure detection value P of the water vapor is read using the pressure sensor 9. Next, in step S13, the target pressure Pi for the detected temperature T is read. Here, the target value Pi is the saturation pressure of water at the detection value T, and is stored in advance. For example, a target value T in which the temperature detection value T is a predetermined temperature ₀ (= 150 ° C.), the target value Pi of the pressure is 0.5 MPa, and there is no need for correction. On the other hand, when the detected value T is higher than the predetermined temperature, the target value Pi of the pressure becomes larger than 0.5 MPa, so that the pressure in the refrigerant layer 6b is increased in order to circulate the wet steam in the refrigerant layer 6b. It is necessary to correct the opening degree β of the pressure control valve 10 so that
[0060]
Therefore, in step S14, the detected value P is compared with the target value Pi obtained from the detected temperature T. In the case of P <Pi, it can be estimated that the steam dryness is 1, and at this time, the cooling efficiency of the steam may decrease and the temperature adjustment of the catalytic reaction layer 6a may be insufficient. There is. Therefore, the process proceeds to step S15, in which the pressure β of the refrigerant layer 6b is increased by decreasing the opening degree β of the pressure control valve 10. As described above, by increasing the pressure of the steam and adjusting it to the saturated steam pressure, the steam temperature can be adjusted to a predetermined temperature, here about 150 ° C. As a result, the dryness becomes smaller than 1, the steam can be composed of a two-phase state of a gas phase and a liquid phase, and the cooling performance of the steam can be maintained.
[0061]
On the other hand, in step S14, when P ≧ Pi, that is, when the steam is wet, it is determined that the steam temperature is appropriate as the refrigerant and the refrigerant performance can be maintained. That is, since the temperature of the catalyst reaction layer 6a can be sufficiently adjusted, the opening degree β of the pressure control valve 10 is changed to the basic opening degree β. ₀ Keep it.
[0062]
By repeating such a control flow every time a load change occurs, it is possible to always allow wet steam having a dryness of less than 1 to flow in the refrigerant layer 6b. When the present flow is repeated every predetermined time (for example, every 10 msec), when the detection value P is compared with the target value Pi in step S14, when P> Pi, the opening β is determined. As the pressure increases, the pressure in the refrigerant layer 6b decreases. This can prevent an excessive liquid phase from being generated in the steam flow, and can secure steam used for the reforming reaction on the downstream side. When P = Pi, the degree of dryness of the steam in the refrigerant layer 6b is maintained at a value smaller than 1 by maintaining the opening degree β.
[0063]
By performing such control, a temperature distribution equivalent to that of the second embodiment can be obtained.
[0064]
Next, effects of the present embodiment will be described. Hereinafter, only the effects different from those of the second embodiment will be described.
[0065]
The dryness determining means compares the predetermined pressure determined according to the temperature of the fluid flowing out of the refrigerant layer 6b with the fluid pressure in the refrigerant layer 6b to determine the dryness of the fluid by the pressure comparing means (S14). Prepare. Further, a pressure adjusting valve 10 for adjusting the fluid pressure in the refrigerant layer 6b is provided as a dryness adjusting means. Here, the pressure target value Pi is obtained from the temperature detection value T detected by the temperature sensor 4, and the dryness of the steam is determined by comparing this with the pressure detection value P. By adjusting the steam pressure in accordance with the determination result, the dryness of the steam is adjusted to a predetermined value. Thus, even when the degree of freedom in adjusting the flow rate of steam is small, the dryness of steam can be adjusted to a predetermined value, and the heat exchange characteristics of steam can be stabilized. As a result, the CO reduction efficiency can be maintained high regardless of the operating conditions.
[0066]
In the present embodiment, the selective oxidation reactor 6 may be replaced with the shift reactor 3.
[0067]
Next, a fourth embodiment will be described. Hereinafter, a description will be given focusing on portions different from the second embodiment.
[0068]
FIG. 7 shows the configuration of the CO reduction device 11 used here. This embodiment is a case where the correction of the steam flow rate in the second embodiment and the correction of the steam pressure in the third embodiment are not performed. Here, by controlling the steam temperature, the dryness of the steam in the refrigerant layer 6b is maintained at a value smaller than 1.
[0069]
A heat exchanger 13 is provided for performing heat exchange between the hydrogen-rich gas flowing through the catalytic reaction layer 6a of the selective oxidation reactor 6 and steam before flowing through the refrigerant layer 6b. In addition, a three-way valve 12 is provided for setting a flow rate ratio of the water vapor generated by a water preheating device (not shown) to be circulated to the heat exchanger 13. A part of the steam supplied from the water preheating device (not shown) is supplied to the heat exchanger 13, and the other flows through a bypass that bypasses the heat exchanger 13 and joins on the downstream side of the heat exchanger 13, It is supplied to the selective oxidation reactor 6. On the downstream side of the refrigerant layer 6b of the selective oxidation reactor 6, a pressure reducing valve 5 is provided so that the pressure in the refrigerant layer 6b can be adjusted. In addition, a temperature sensor 4 is provided between the refrigerant layer 6b and the pressure reducing valve 5, so that the temperature of steam discharged from the refrigerant layer 6b can be detected.
[0070]
Next, the hydrogen-rich gas system 15 and the steam system 17 in the CO reduction device 11 having such a configuration will be described.
[0071]
The hydrogen-rich gas is supplied to the catalytic reaction layer 6a of the selective oxidation reactor 6 after air whose flow rate is adjusted by an air supply device (not shown) is mixed. In the catalyst reaction layer 6a, a selective oxidation reaction of CO occurs with heat generation. The hydrogen-rich gas flowing out of the catalytic reaction layer 6a flows through the hydrogen-rich gas flow path of the heat exchanger 13 and exchanges heat with steam flowing through the steam flow path before being supplied to the fuel cell.
[0072]
On the other hand, when the steam is generated by a water preheating device (not shown), it is supplied to the three-way valve 12. The three-way valve 12 is divided into a path in which steam passes through the heat exchanger 13 and a path in which the steam bypasses the heat exchanger 13. The steam passing through the heat exchanger 13 absorbs heat from the hydrogen-rich gas, merges with the wet steam bypassing the heat exchanger 13, and then flows into the refrigerant layer 6b. The three-way valve 12 sets the opening degree γ to 1 when the flow rate bypassing the heat exchanger 13 is zero, and sets the opening degree γ to 0 when the flow rate that does not bypass the heat exchanger 13 is zero. The opening degree γ of the three-way valve 12 is adjusted according to the value of the temperature of the combined steam detected by the temperature sensor 4.
[0073]
A method of correcting the opening degree γ of the three-way valve 12 will be described with reference to a flowchart shown in FIG. This flow is repeatedly performed at predetermined time intervals during a load transition period in which the operating load fluctuates, thereby maintaining the dryness of steam at a value smaller than 1. After the end of the operating load transition period, the opening γ of the three-way valve 12 is set to a predetermined opening according to the operating load.
[0074]
In step S21, the detection value T of the temperature sensor 4 is read. In step S22, the detected value T and the target value T ₀ Compare with Here, the target value T ₀ Is a temperature at which the dryness of steam does not become 1 and is suitable as a refrigerant. Target value T ₀ Is preferably the boiling point of water. However, in this embodiment, since it is not desired to discharge a large amount of unvaporized water in the subsequent process, the target value T ₀ Is slightly higher than the boiling point of water. Specifically, the pressure is increased by the pressure reducing valve 5, for example, 160 ° C., which is slightly higher than the boiling point at 150 MPa at about 0.5 MPa.
[0075]
In step S22, T <T ₀ Is determined, the degree of dryness of the steam is small, and there is a possibility that a large amount of unvaporized water exists. Therefore, the process proceeds to step S23, and the opening degree γ is increased. Thereby, the ratio of the steam flowing through the heat exchanger 13 is increased, and the steam temperature is increased. As a result, unvaporized water can be reduced, and steam can be used for the fuel reforming reaction. This corresponds to, for example, a transition period in which the operating load increases.
[0076]
On the other hand, in step S22, T> T ₀ Is determined, the dryness of the steam is 1 and the cooling performance of the steam is degraded. That is, the degree of superheat of the steam is excessive, and the temperature adjustment of the catalyst reaction layer 6a may be insufficient. Thus, the steam temperature is reduced by reducing the opening γ of the three-way valve 12 to reduce the ratio of the steam flowing through the heat exchanger 13. This corresponds to, for example, a transition period in which the operating load decreases.
[0077]
On the other hand, in step S22, T = T ₀ If determined, the process proceeds to step S25. At this time, the state of the temperature and the degree of dryness of the steam flowing through the refrigerant layer 6b is determined to be appropriate, and the opening degree γ of the three-way valve 12 is maintained. This corresponds to, for example, a case where the fluctuation of the operation load is gentle.
[0078]
When the temperature of the steam flowing through the refrigerant layer 6b is adjusted by adjusting the opening degree γ of the three-way valve 12 as described above, the present flow ends. By repeatedly performing such control, the steam can be maintained at a temperature suitable for the refrigerant, and the dryness of the steam in the refrigerant layer 6b can be maintained smaller than 1.
[0079]
Note that the temperature distribution of the present embodiment can be shown in the same manner as in the second embodiment.
[0080]
Next, effects of the present embodiment will be described. Hereinafter, only portions different from the second embodiment will be described.
[0081]
Heating means for heating the fluid flowing into the refrigerant layer 6b is provided as a temperature adjusting means. Thereby, even when the degree of freedom in adjusting the flow rate and pressure of the fluid is small, the dryness of the fluid can be adjusted to a predetermined value, and the CO reduction efficiency is maintained by stabilizing the heat exchange characteristics of the refrigerant layer 6b. can do.
[0082]
Here, as the heating means, a heat exchanger 13 for performing heat exchange between the fluid flowing through the refrigerant layer 6b and the hydrogen-rich gas, and a three-way valve 12 for adjusting a rate at which the fluid bypasses the heat exchanger 13 are provided. Prepare. Thereby, the flow rate of steam flowing through the heat exchanger 13 can be adjusted, and the heating amount of steam can be adjusted to a predetermined value. As a result, the dryness of the steam can be reliably adjusted, so that the CO reduction efficiency can be maintained at a high efficiency.
[0083]
In the present embodiment, steam is used as the refrigerant, but other fluids may be used. For example, a hydrocarbon-based fuel that is a reforming raw material may be used. Alternatively, heat exchange may be performed between another refrigerant and the catalytic reaction layer 3a, and further heat exchange may be performed between the refrigerant and the reforming raw material.
[0084]
As described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a catalytic reaction device used in a first embodiment.
FIG. 2 is a flowchart of steam flow rate control in the first embodiment.
FIG. 3 is a diagram showing an internal temperature distribution in the first embodiment.
FIG. 4 is a schematic configuration diagram of a catalytic reaction device used in a second embodiment.
FIG. 5 is a schematic configuration diagram of a catalytic reaction device used in a third embodiment.
FIG. 6 is a flowchart of steam flow rate control in a third embodiment.
FIG. 7 is a schematic configuration diagram of a catalytic reactor used in a fourth embodiment.
FIG. 8 is a flowchart of water vapor flow rate control in a fourth embodiment.
[Explanation of symbols]
2 Flow control valve (flow control means)
3 shift reactor
3a Catalyst reaction layer
3b Refrigerant layer
6 Selective oxidation reactor
6a Catalyst reaction layer
6b Refrigerant layer
10 Pressure control valve (pressure control means)
12 Three-way valve (flow rate adjusting means)
13 heat exchanger (heat exchange means)
S2, S22: Temperature comparison means
S14: Pressure comparison means

Claims (11)

A catalytic reaction layer that generates an exothermic reaction using the supplied reaction gas,
A fluid circulates through the inside, a refrigerant layer capable of heat exchange with the catalyst reaction layer,
Dryness determination means for determining the dryness of the fluid flowing through the refrigerant layer,
And a dryness adjusting means for adjusting the dryness of the fluid based on the determination result of the dryness. 2. The catalytic reformer for a fuel reforming system according to claim 1, further comprising a temperature comparison unit configured to determine a dryness of the fluid by comparing a temperature of the fluid flowing out of the refrigerant layer with a predetermined temperature as the dryness determination unit. 3. . 3. The temperature controller according to claim 1, further comprising a temperature controller configured to adjust a temperature of the fluid such that a temperature of the fluid flowing out of the refrigerant layer has a predetermined value equal to or higher than a phase change temperature of the fluid. 4. Catalytic reactor for fuel reforming system. 4. The catalytic reactor for a fuel reforming system according to claim 3, further comprising a flow rate adjusting unit that adjusts a flow rate of a fluid flowing through the refrigerant layer as the temperature adjusting unit. 5. 4. The catalytic reactor for a fuel reforming system according to claim 3, further comprising a heating unit configured to heat the fluid flowing into the refrigerant layer, as the temperature control unit. 5. As the heating unit, a heat exchange unit that performs heat exchange between the fluid flowing through the refrigerant layer and the hydrogen-rich gas,
The catalytic reaction device for a fuel reforming system according to claim 5, further comprising: a flow rate ratio adjusting unit that adjusts a ratio of the fluid that bypasses the heat exchange unit. The dryness determination means includes a pressure comparison means for determining a dryness of the fluid by comparing a predetermined pressure determined according to a temperature of the fluid flowing out of the refrigerant layer with a fluid pressure in the refrigerant layer. ,
2. The catalytic reactor for a fuel reforming system according to claim 1, further comprising a pressure adjusting unit that adjusts a fluid pressure in the refrigerant layer as the dryness adjusting unit. 3. The catalyst reaction device for a fuel reforming system according to claim 1, wherein carbon dioxide and hydrogen are generated by a reaction between carbon monoxide and water in the catalyst reaction layer. The catalyst reaction device for a fuel reforming system according to any one of claims 1 to 7, wherein in the catalyst reaction layer, carbon dioxide is generated by a reaction between carbon monoxide and oxygen. The catalytic reactor for a fuel reforming system according to any one of claims 1 to 9, wherein steam serving as a raw material for generating a hydrogen-rich gas is circulated in a gas-liquid two-phase state as a fluid flowing through the refrigerant layer. A catalytic reaction layer capable of removing carbon monoxide,
A fluid circulates through the inside, comprising a refrigerant layer capable of heat exchange with the catalyst reaction layer,
A catalytic reactor for a fuel reforming system, wherein a degree of dryness of a fluid flowing through the refrigerant layer is adjusted so that the refrigerant layer is maintained at a temperature suitable for reaction efficiency.

Images